1. Field of the Invention
The present invention relates to a welded differential device for vehicles.
2. Description of the Prior Art
In a conventional differential device for automobiles and the like, the differential casing has been cast as an integral shell. The fitting of a ring gear to the differential casing has been done by integrally forming a ring gear-fitting flange around the differential casing on casting, boring bolt holes in the flange, providing screw holes in the ring gear, and assembling bolts through the bolt holes in the flange and into the screw holes in the ring gear. This method of assembly has been used because a cast differential casing has not been adaptable to welding. The supporting of the pinion shaft by the differential casing has been done by boring a pair of pinion shaft holes at opposed positions in the differential casing, fitting the pinion shaft into these holes and then providing anti-slipout pins.
The conventional differential device of such arrangement has the following demerits. Since the differential casing is integrally formed, it is difficult to assemble the gearing in the differential casing. Furthermore, since a fitting flange for the ring gear has to be integrally provided in the differential casing and this flange has to be sufficiently strong, the differential casing is necessarily extremely heavy. Since screw holes for the fitting bolts have to be provided in the ring gear, the ring gear has to be made thick, resulting in an increased mass of the gear. The presence of screw holes is likely to make the strain in the heat treatment of the ring gear uneven. Since a large number of bolt holes and screw holes have to be worked, the number of work steps is increased. Moreover, an anti-slipout means for the bolts, such as a lockplate, has to be provided. The pinion shaft support of the differential casing, which is subjected to a heavy load by the pinion shaft, is liable to be deformed or damaged, and to prevent such deformation or damage, the differential casing as a whole has to be made thick such that the weight thereof increases. The pinion shaft and the differential casing need pins for prevention of the pinion shaft from slipping out and this leads to a still more complicated configuration and increased weight of the device.